Traditional treadboard of treadmill is usually applied with a flat board, the belt of the treadmill moves on the flat board, as the flat board is rigid, the feet of the running sportsman hard contacts on the treadboard, which hurts the knee and the ankle joints of the sportsman. Existing treadboard of the treadmill is usually applied with springs or elastic rubber body below the treadboard to buffer the flat board, however, the treadboard is a single configuration that the sportsman still hard contacts instantly when stamping on the treadboard. A new treadboard is disclosed in the Chinese patent database with publishing number CN203469310U, the flat board is replaced by an arc structural board, so that the entire board is transformed when a sportsman is stamping on the treadboard, however, in this case, the sportsman still hard contacts on the treadboard instantly when stamping on the treadboard, above problem still happens; besides, when assembling, as one end of the arc structure has to be movable so as to move to the another movable end, thus making it complicated and inconvenient to assemble.